It is usual in many industries to transport goods in stacks of receptacles, the stacks being loaded on wheeled dollies. The loaded dollies are usually transported from the factory, for example, to warehouses or retail outlets, on trucks. It is important, in order to facilitate the distribution of the goods, that the loaded dollies be freely movable onto the trucks at the factory, and that the loaded dollies be freely movable off the trucks at the warehouse or retail centers. It is also most important that the loaded dollies be firmly and securely retained in place on the trucks as they are being transported from one location to another, and that this be achieved by appropriate means which does not entail excessive extraneous operations in order to secure the loaded dollies in the trucks, and subsequently to release the loaded dollies when the destinations are reached.
A security system is described in the copending application Ser. No. 545,115 which is eminently suited for the purpose described in the preceding paragraph. The system described in the copending application comprises a series of gates which are mounted on upright posts adjacent the two side walls of the truck. A central aisle is provided between the gates to permit the dollies to be wheeled onto the truck and into positions along the side wall in which they are securely retained by the gates until the destination is reached. Then, the gates may be opened, and the dollies may be conveniently, individually wheeled off the truck.
The security system of the present invention is of the general type as the one described in the copending application. In the system of the present invention, the gates are in the form of U-shaped slide bars which may be conveniently moved upwardly along channels in corresponding pairs of the upright posts to positions in which they permit the dolly to be moved between the posts and tack against the side walls of the truck. The slide bar gates may then be moved down the channels to closed and locked positions in which they engage the receptacles loaded on the various dollies between the corresponding pairs of posts, so as to retain the loaded dollies firmly and securely against the side walls of the truck. When a destination is reached, the individual slide bars are moved upwardly to their open positions, so that the loaded dollies may be easily and readily be individually removed from the truck along the central aisle .